The present invention relates, in general, to an exhaust gas system.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
In multi-cylinder internal combustion engines, exhaust from the individual cylinders is brought together in exhaust collecting devices. Prior art examples include exhaust manifolds and turbocharger constructions of single-piece configuration to save costs for a bolted connection, as disclosed in U.S. Pat. No. 6,256,990 to Itoh. This means that the same material must be used for the exhaust manifold and the turbocharger, oftentimes a high-alloy special steel. As the material selection focuses always on the weakest link in the entire module, the cost factor is therefore significant. Another drawback involves the high total weight of cast manifold turbocharger modules because certain wall thicknesses of cast constructions cannot fall below a minimum, as opposed to sheet metal constructions.
Published U.S. Pat. Appl. No. 2007/0289954 to Bien et al. describes an exhaust manifold and a turbocharger housing of multipart configuration which are welded together. The exhaust manifold is designed as an airgap-insulated exhaust manifold. Although material costs for the exhaust gas system can be lowered and weight can be saved, still the weld seam zone between the exhaust manifold and the turbocharger housing represents a strength weak point from a thermomechanical standpoint.
It would therefore be desirable and advantageous to provide an improved exhaust gas system which obviates prior art shortcomings and which exhibits superior thermomechanical strength and high rigidity while at the same time being lightweight and yet reliable in operation.